5 ms·
> if the baseline chance of delay is 10%, engineering works add 25%, strikes add 35%, and bad weather adds 20%, then when all these problems happen, there's a 9
by zfnmxt 2y ago
> if the baseline chance of delay is 10%, engineering works add 25%, strikes add 35%, and bad weather adds 20%, then when all these problems happen, there's a 90% chance your train will be delayed.
What if signal failures "add" 15%? Then all factors combined would mean that there's a 105% chance your train will be delayed!
Adding up probabilities like this doesn't make sense. If you simplify these things as independent events, the probability of delay is just the 1 minus the product of all the probabilities of each event not happening (i.e., 1 - P(event)).
As for the article---I think you really undervalue your time and the price of inconvenience. I can see how you can romanticize it as a nice way to get things done, but (dealing with) train delays is hardly distraction free and is full of forced setting changes and (very) shit working environments (like waiting on a platform). This is a bad deal, even if it's free. Money is there to to be spent; this is a instance in which to spend it, moral/ethical/fraud concerns aside.
But hey maybe you're a Von Neuman type and thrive in cacophony and chaos.
- Aeolun 2y agoMost of these trains are one and done things straight from the departure station to London? The only experience I have was taking them in the other direction though, because I opted for a flight instead of dealing with it again to go back to London. Was a new experience booking a train ticket and seeing a quote of £250. I thought the machine was broken.
- MathMonkeyMan 2y agoYour comment made me wonder. 65% chance of delay. >>> s = 'if the baseline chance of delay is 10%, engineering works add 25%, strikes add 35%, and bad weather adds 20%' >>> pb = 0.1 >>> pe = 0.25 >>> ps = 0.35 >>> pw = 0.2 >>> p = 1 - (1 - pb)*(1 - pe)*(1 - ps)*(1 - pw) >>> p 0.649
- ValentineC 2y ago> As for the article---I think you really undervalue your time and the price of inconvenience. I can see how you can romanticize it as a nice way to get things done, but (dealing with) train delays is hardly distraction free and is full of forced setting changes and (very) shit working environments (like waiting on a platform). By delays, I think the author meant that they get on a train, then sit in it for ~5 hours, with the option of paying roughly twice the price for first class [1]. As someone who frequently uses their laptop on public transport too, this sounds like a great way to either get things done or pass time. [1] https://www.avantiwestcoast.co.uk/travel-information/onboard/first-class https://www.avantiwestcoast.co.uk/travel-information/onboard...
- Doctor_Fegg 2y agoThough the problem is that delayed trains are often overcrowded trains. And overcrowded trains are not conducive for doing work on a laptop, unless you like sitting on the vestibule floor outside the toilet door with your laptop on your knees.
- tempfile 2y agoTo be fair, in my experience a lot of train operators will not declassify a train unless it is very very full. So if you got a first class ticket, you wouldn't be as stuck.
- ValentineC 2y ago> Though the problem is that delayed trains are often overcrowded trains. I've experienced exactly this with Deutsche Bahn trains, but I've been looking at the National Rail Conditions of Travel [1], and there's no requirement that tickets automatically turn into "flexi" tickets, allowing use of alternate routes, unlike German regulations. I'm guessing a huge number of people being allowed to hop onto the next train instead of just being provided a refund is a huge cause of overcrowding, but I also haven't experienced the UK rail system first-hand in many years. [1] https://assets.nationalrail.co.uk/e8xgegruud3g/3Y9UXuFziljwsGFCUAwKAA/0aa50a101febffda28c070aae2572570/National_Rail_Conditions_of_Travel.pdf#page=20 https://assets.nationalrail.co.uk/e8xgegruud3g/3Y9UXuFziljws...
- sveme 2y agoSir, this is an Englishman writing; he‘s obviously taking the piss.
- WindyMiller 2y agoI think you really undervalue the pleasure of getting one over on our awful train system, and also overestimate how much money the young people of the UK have access to.
- tempfile 2y agoFor small probabilities it works :) 1-(1-p1)(1-p2) = p1+p2-p1p2 and a similar formula holds for more terms. so neglecting terms of order p^2 gives the form in the article
- sebastiennight 2y agoFor probabilities (much) smaller than 10%, sure. But adding 10%, 20%, and 35%, is already a pretty bad start. The error rate becomes huge. (in the article example, the 10% estimate of chances of being on time is ~3.5 smaller than the actual 35% correct result). Being wrong by half an order of magnitude, is being quite wrong :)
- tempfile 2y agoI'm not disagreeing with you!